Muraki Katsuhiko, Iwata Yuko, Katanosaka Yuki, Ito Tomohiro, Ohya Susumu, Shigekawa Munekazu, Imaizumi Yuji
Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya 467-8603 Japan.
Circ Res. 2003 Oct 31;93(9):829-38. doi: 10.1161/01.RES.0000097263.10220.0C. Epub 2003 Sep 25.
Changes in membrane tension resulting from membrane stretch represent one of the key elements in blood flow regulation in vascular smooth muscle. However, the molecular mechanisms involved in the regulation of membrane stretch remain unclear. In this study, we provide evidence that a vanilloid receptor (TRPV) homologue, TRPV2 is expressed in vascular smooth muscle cells, and demonstrate that it can be activated by membrane stretch. Cell swelling caused by hypotonic solutions activated a nonselective cation channel current (NSCC) and elevated intracellular Ca2+ ([Ca2+]i) in freshly isolated cells from mouse aorta. Both of these signals were blocked by ruthenium red, an effective blocker of TRPVs. The absence of external Ca2+ abolished this increase in [Ca2+]i caused by the hypotonic stimulation and reduced the activation of NSCC. Significant immunoreactivity to mouse TRPV2 protein was detected in single mouse aortic myocytes. Moreover, the expression of TRPV2 was found in mesenteric and basilar arterial myocytes. Treatment of mouse aorta with TRPV2 antisense oligonucleotides resulted in suppression of hypotonic stimulation-induced activation of NSCC and elevation of [Ca2+]i as well as marked inhibition of TRPV2 protein expression. In Chinese hamster ovary K1 (CHO) cells transfected with TRPV2 cDNA (TRPV2-CHO), application of membrane stretch through the recording pipette and hypotonic stimulation consistently activated single NSCC. Moreover, stretch of TRPV2-CHO cells cultured on an elastic silicon membrane significantly elevated [Ca2+]i. These results provide a strong basis for our purpose that endogenous TRPV2 in mouse vascular myocytes functions as a novel and important stretch sensor in vascular smooth muscles.
由膜拉伸引起的膜张力变化是血管平滑肌血流调节的关键因素之一。然而，参与膜拉伸调节的分子机制仍不清楚。在本研究中，我们提供证据表明，一种香草酸受体（TRPV）同源物TRPV2在血管平滑肌细胞中表达，并证明它可被膜拉伸激活。低渗溶液引起的细胞肿胀激活了新鲜分离的小鼠主动脉细胞中的非选择性阳离子通道电流（NSCC）并升高了细胞内Ca2+（[Ca2+]i）。这两种信号均被TRPVs的有效阻滞剂钌红阻断。细胞外Ca2+的缺失消除了低渗刺激引起的[Ca2+]i升高，并降低了NSCC的激活。在单个小鼠主动脉肌细胞中检测到对小鼠TRPV2蛋白的显著免疫反应性。此外，在肠系膜和基底动脉肌细胞中发现了TRPV2的表达。用TRPV2反义寡核苷酸处理小鼠主动脉导致低渗刺激诱导的NSCC激活和[Ca2+]i升高受到抑制，以及TRPV2蛋白表达受到明显抑制。在用TRPV2 cDNA转染的中国仓鼠卵巢K1（CHO）细胞（TRPV2-CHO）中，通过记录微管施加膜拉伸和低渗刺激一致地激活了单个NSCC。此外，在弹性硅膜上培养的TRPV2-CHO细胞的拉伸显著升高了[Ca2+]i。这些结果为我们的观点提供了有力依据，即小鼠血管肌细胞中的内源性TRPV2在血管平滑肌中作为一种新的重要拉伸传感器发挥作用。
